Setting SSI variables from configuration

[Attila Nagy]

Hi,

I have an SSI page with the following in it:
<!--#if expr="$CRAN_HOST" -->
   <!--#echo  encoding="none" var="CRAN_HOST"--><br>
<!--#endif -->

I would like to set CRAN_HOST to a given value, but I couldn't find any 
ways of doing this with nginx.
Any ideas?

Thanks,